- Volume 69, Issue 8, 2020

Introduction. Acinetobacter baumannii is a critical priority pathogen listed by the World Health Organization due to increasing levels of resistance to carbapenem classes of antibiotics. It causes wound and other nosocomial infections, which can be life-threatening. Hence, there is an urgent need for the development of new classes of antibiotics.

Aim. To study the interaction of carabapenems with class D beta-lactamases (oxacillinases) and analyse drug resistance by studying enzyme–substrate complexes using modelling approaches as a means of establishing correlations with the phenotypic data.

Methodology. The three-dimensional structures of carbapenems (doripenem, ertapenem, imipenem and meropenem) were obtained from DrugBank and screened against class D beta-lactamases. Further, the study was extended with their variants. The variants’ structure was homology-modelled using the Schrödinger Prime module (Schrödinger LLC, NY, USA).

Results. The first discovered intrinsic beta-lactamase of Acinetobacter baumannii , OXA-51, had a binding energy value of −40.984 kcal mol−1, whereas other OXA-51 variants, such as OXA-64, OXA-110 and OXA-111, have values of −60.638, –66.756 and −67.751 kcal mol−1, respectively. The free energy values of OXA-51 variants produced better results than those of other groups.

Conclusions. Imipenem and meropenem showed MIC values of 2 and 8 µg ml−1, respectively against OXA-51 in earlier studies, indicating that these are the most effective drugs for treatment of A. baumannii infection. According to our results, OXA-51 is an active enzyme that shows better interactions and is capable of hydrolyzing carbapenems. When correlating the hydrogen-bonding interaction with MIC values, the predicted results are in good agreement and might provide initial insights into performing similar studies related to OXA variants or other antibiotic–enzyme-based studies.

Introduction. Linezolid-resistant (LZR) Staphylococcus capitis has recently emerged in our hospital, and its potential resistance mechanisms are still not clear.

Aim. This study aimed to investigate the epidemiology, clinical and genetic characteristics, resistance mechanisms and biofilm formation capacity of LZR S. capiti s isolated from patients at Huashan Hospital, Shanghai, PR China between 2012 and 2018.

Methodology. Strains were subjected to antimicrobial susceptibility testing (AST) with antibiotics using the broth microdilution method according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. The presence of cfr, optrA and poxtA, as well as mutations in the 23S ribosomal (r)RNA and ribosomal proteins, was investigated using PCR and sequencing techniques. The genetic relationship between isolates was analysed using pulsed-field gel electrophoresis (PFGE) and whole-genome sequencing (WGS). Biofilm biomasses were detected by using crystal violet staining.

Results. Twenty-one LZR S. capitis strains displayed MICs of 32–512 μg ml−1. All LZR strains showed G2576T and C2104T mutations in the 23S rRNA V region. Besides G2576T and C2104T, no base mutations were detected in the V region. The cfr was detected in 12 strains, while optrA and poxtA were not amplified in 21 S . capitis strains. PFGE showed that the LZR S. capitis strains belonged to a single clone. The phylogenetic tree showed that 20 LZR S. capitis strains were highly similar to LNZR-1, isolated from Harbin (located in the north of China) in 2013, which showed resistance to linezolid.

Conclusions. In this research, cfr-negative strains displayed linezolid MICs of 32 μg ml−1. In comparison, cfr-positive strains exhibited linezolid MICs of 128–512 μg ml−1, indicating that high levels of linezolid resistance appear to be related to the presence of cfr. The outbreak of LZR S. capitis in our hospital needs to be monitored closely.

Introduction. The bla CTX-M-3 gene has rarely been reported in Morganella morganii strains and its genetic environment has not yet been investigated.

Aim. To identify the bla CTX-M-3 gene in M. morganii isolated from swine and characterize its genetic environment.

Methodology. A M. morganii isolate (named MM1L5) from a deceased swine was identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and subjected to antimicrobial susceptibility testing. The bla genes were detected and then the genetic location and environment of bla CTX-M-3 were investigated by Southern blot and PCR mapping, respectively. The M. morganii bla CTX-M-3 gene was cloned and expressed in Escherichia coli .

Results. Isolate MM1L5 harboured the bla CTX-M-3 and bla TEM-1 genes. The bla CTX-M-3 gene, located on the chromosome, was co-carried with an IS26 and bla TEM-1 gene by a novel 6361 bp IS26-flanked composite transposon, designated Tn6741. This transposon consisted of a novel bla CTX-M-3-containing module, IS26-ΔISEcp1-bla CTX-M-3-Δorf477-IS26 (named Tn6710), and a bla TEM-1-containing module, IS26-Δorf477-bla TEM-1-tnpR-IS26, differing from previous reports. Phylogenetic analysis showed a significant variation based on the sequence of Tn6741, as compared to those of other related transposons. Interestingly, although the cloned bla CTX-M-3 gene could confer resistance to ceftiofur, cefquinome, ceftriaxone and cefotaxime, one amino acid substitution (Ile-142-Thr) resulted in a significant reduction of resistance to these antimicrobials.

Conclusion. This is the first time that bla CTX-M-3 has been identified on a chromosome from a M. morganii isolate. Furthermore, the bla CTX-M-3 gene was located with an IS26 element and bla TEM-1 gene on a novel IS26-flanked composite transposon, Tn6741, suggesting that Tn6741 might act as a reservoir for the bla CTX-M-3 and bla TEM-1 genes and may become an important vehicle for their dissemination among M. morganii .

Introduction. Periprosthetic joint infections caused by methicillin-resistant Staphylococcus aureus (MRSA-PJIs) are rare, with only a few studies reporting the treatment outcomes and even fewer reporting outcomes with one-stage exchange.

Aim. This study aims to analyse the outcomes of one-stage exchange in the management of MRSA-PJIs.

Methodology. Patients with MRSA-PJI of the hip and knee, who were treated with a one-stage exchange between 2001 and 2018 were enrolled in this study. The final cohort comprised of 29 patients, which included 23 hips and six knees. The mean follow-up was 5.3 years (1–9 years). Reinfection and complications rates after the one-stage exchange were analysed.

Results. Overall infection control could be achieved in 93.1 % (27 out of 29 patients). The overall revision rate was 31.0% (9 patients), with three patients requiring an in-hospital revision (10.3 %). Six patients had to be revised after hospital discharge (20.7 %). Of the two reinfections, one had a growth of MRSA while the other was of methicillin-sensitive Staphyloccocus epidermidis.

Conclusion. One-stage exchange surgery using current techniques could improve surgical outcomes with excellent results in the management of MRSA-PJIs.

Introduction. Coronavirus disease 2019 (COVID-19) is an infectious disease caused by Severe Acute Respiratory Corona Virus-2 (SARS-CoV-2). The disease was first identified in December 2019 in Wuhan, the capital of China's Hubei province, and has since spread globally, resulting in the ongoing 2019–2020 corona virus pandemic. SARS-CoV-2 is closely related to the original SARS-CoV. It is thought to have a zoonotic origin. The virus is primarily spread between people during close contact, often via small droplets produced by coughing, sneezing or talking. People may also become infected by touching a contaminated surface and then touching their face. COVID-19 patients currently remain the primary source of infection. An epidemiological survey indicated that the general population is susceptible to SARS-CoV-2. The spectrum of this disease ranges from mild to life-threatening. Fever is the most common symptom, although older people and those with comorbidities may experience fever later in the disease. Other common symptoms include cough, loss of appetite, fatigue, shortness of breath, sputum production, and muscle and joint pains. Symptoms such as nausea, vomiting and diarrhea have been observed in varying percentages. Some cases might progress promptly to acute respiratory distress syndrome (ARDS) and/or multiple organ function failure. Asymptomatic carriers and those in the incubation period may also be infectious.

Aim. To determine the epidemiological and clinical characteristics of patients presenting with COVID-19 at the screening clinic of a tertiary care hospital in Peshawar, Pakistan.

Methodology. In this descriptive study, we analysed data of patients presenting to a newly established Covid-19 screening clinic in Rehman Medical Institute. Anyone who reported with new onset fever and/or cough was tested for SARS-CoV-2 in the screening clinic. We documented and analysed demographic, epidemiological and clinical characteristics, which included age, sex, travel history, clinical features, comorbidities and laboratory data of patients confirmed by real-time reverse-transcription (RT)-PCR at Rehman Medical Institute, Peshawar, Pakistan from 15 March till 21 April 2020. Paired specimens of throat swabs and nasal swabs were obtained from 845 patients, ribonucleic acid (RNA) was extracted and tested for SARS-CoV-2 by the RT-PCR assay.

Results. A total of 845 specimens were taken as described above. The positive rate for SARS-CoV-2 was about 14.3%. Male and older population had a significantly higher positive rate. Of the 121 patients infected with SARS-CoV-2, the mean age was 43.19 years (sd, 17.57) and the infections were more frequent among male gender accounting for 85 (70.25 %) patients. Common symptoms included fever (88 patients, 72 %), cough (72 patients, 59.5 %) and shortness of breath (69 patients, 57 %). Twenty-two (18 %) patients had recent travel history outside Pakistan in the previous 14 days, the majority of whom had returned back from Saudi Arabia.

Conclusion. In this single-centre, prospective, descriptive study, fever, cough and shortness of breath were the most common symptoms. Old age (>50 years), chronic underlying comorbidities and travel history may be risk factors. Therefore, we concluded that viral nucleic acid amplification tests (NAAT) played an important role in identifying SARS-CoV-2 infection in a screening clinic, which helped with isolation and cohorting of these patients.